Interpretive Summary: A sire-maternal grandsire (MGS) threshold model was used for genetic evaluation of stillbirth in US Holsteins. Data consisted of almost 7.5 million records, and over 41,000 AI bulls received evaluations. The model included effects of herd-year, year-season, parity-sex, sire, birth year group of sire, MGS, and birth year group of MGS, and dystocia score. Herd-year, sire, and MGS were random effects. Mean PTA, expressed as expected percentage of stillbirths in heifers, were 12.47 and 14.28 for direct and maternal stillbirth, respectively. Reliabilities for the direct and maternal effects averaged 0.53 and 0.52, respectively. Dystocia scores had a larger effect on stillbirth than year-season, sire, or MGS effects. Correlations among US and Interbull stillbirth solutions on the underlying scale for bulls with at least 90% reliability ranged from 0.63 to 0.90 across countries for direct SB and 0.69 to 0.96 for maternal SB, indicating that results were generally consistent with those from other countries. There was no evidence of a consistent genetic trend. More complete recording of stillbirth scores would improve reliabilities and possibly allow for evaluations of other breeds.

Technical Abstract:
A sire-maternal grandsire (MGS) threshold model was used for genetic evaluation of stillbirth in US Holsteins. Data consisted of almost 7.5 million records, and over 41,000 AI bulls received evaluations. The model included effects of herd-year, year-season, parity-sex, sire, birth year group of sire, MGS, and birth year group of MGS, and dystocia score. Herd-year, sire, and MGS were random effects. Mean PTA, expressed as expected percentage of stillbirths in heifers, were 12.47 and 14.28 for direct and maternal stillbirth, respectively. Reliabilities for the direct and maternal effects averaged 0.53 and 0.52, respectively. Dystocia scores had a larger effect on stillbirth than year-season, sire, or MGS effects. Correlations among US and Interbull stillbirth solutions on the underlying scale for bulls with at least 90% reliability ranged from 0.63 to 0.90 across countries for direct SB and 0.69 to 0.96 for maternal SB, indicating that results were generally consistent with those from other countries. There was no evidence of a consistent genetic trend. More complete recording of stillbirth scores would improve reliabilities and possibly allow for evaluations of other breeds.